Photographic emulsions, layers and elements



United States Patent C) 3,252,801 PHOTOGRAPHIC EMULSIONS, LAYERS ANDELEMENTS Abraliam Bernard (Iohen, Springfield, and Comer Drake Thisinvention relates to improved photographic silver halide emulsions,emulsion layers, and film elements embodying the same which are usefulfor continuous tone reproduction in the graphic arts industry.

Photographic films for use in the graphic arts should have gooddimensional stability so that when several films are overlaid, as iscustomary in color reproduction, these films will be in register, i.e.,in exact correspondence. To achieve a high degree of dimensionalstability the photographic emulsions are often coated on glass plates.More recently, hydrophobic film bases, e.g., polyethylene terephthlate,have been used for these purposes in place of glass but the base doesnot solve emulsion shortcomings.

An undesirable characteristic of presently available graphic arts filmsis the change in image optical density which occurs from the Wet to drystate. In practical use, it is usually desirable to develop the film tothe required optical density as determined by inspection or in adensitometer while the iihn is Wet; then to stop the development. Thisis not an accurate method because of the inherent optical densitychanges that occur on drying and it is often necessary to run adevelopment series to obtain a single negative with a desired opticaldensity balance. Moreover, the magnitude of change in wet-to-drydensities will vary with drying conditions. The previous methods are, ofcourse, costly and time consuming.

A desirable characteristic of graphic arts films is their ability tobereduced in image density after development by mechanically removing aportion of the silver image in a controlled fashion by means of a knife,a process commonly referred to as knife etching. Unlike chemicaletching, the cohesive and adhesive properties of the binder play a vitalrole in determining the degree of control possible in knife etching andthe freedom from flaking, cracking, or anchorage failure.

A-tempts have been made to substitute synthetic binders for gelatin inorder to improve its characteristics for graphic arts uses, but thesehave been only partially successful due to the unique photographic andcolloidchernical properties of gelatin as a binder. Improvements in oneproperty are usually at the expense of another and often more importantproperty. Bolton U.S. Patent 2,495,918, for example, suggests replacingthe gelatin in a gelatino-silver halide emulsion with apoly-N-vinyllactam such as poly-N-vinylcaprolactam. Such emulsions,while useful, do not possess the outstanding advantages which have madegelatin the protective colloid in the emulsion making art for manyyears. It is difficult, for instance, to coat such poly-N-vinyllactamemulsions and to obtain a layer of satisfactory hardness and stability.This is particularly true when the exposed element contains the usualphotographic hardeners and is placed in aqueous photographic processingsolutions. Hosmer U. S. Patent 2,754,245 discloses using theinterhalogen adducts of polyvinylpyrrolidone as a gelatin extender inphotographic emulsions but it is difficult to control the all-importanthalogen content of the system with such adducts. Many other bindermodifications have been suggested but none of these provide a properbalance between the major physical and photographic properties requiredin graphic arts films.

An object of this invention is to provide a unique photographic silverhalide emulsion and emulsion layer which retains the advantages ofgelatin while overcoming certain disadvantages. Another object is toprovide photographic emulsion layers and elements for the graphic artsindustry which have improved dimensional stability. Another object is toprovide photographic emulsion layers of improved dimensional stabilityin which the optical density of the developed image remains stableduring change from a wet to a dry state. A further object is to preparesuch emulsion layers which have improved knife etchability, impactstrength, and adherence to a dimensionally stable photographic filmbase. Still other objects will appear hereafter.

The improved gelatino-silver halide emulsions of this invention comprise(1) an aqueous phase containing therein as a part of said phase (a)gelatin and (b) a water-soluble polyvinyl pyrrolidone having an averagemolecular weight of at least 8000 (preferably from 10,000 to 150,000)and (2) a non-aqueous phase dispersed therein of water-dispersiblecolloidal particles (preferably of an average diameter of less than 400mp.) of a substantially water-insoluble vinyl addition polymer of anethylenically unsaturated monomer of molecular weight less than 250,said gelatin, polyvinyl pyrrolidone and Water-insoluble polymer beingpresent in the percentages by weight from 30% to 6% to 30%, and 10% to55%, respectively, of the total weight of the three polymeric binders.There may be present minor amounts, usually less than 5% of the weightof the three binders, of various emulsion adjuvants, dispersing agents,coating aids, etc.

The novel tri-component colloid binder silver halide emulsions can bemade in various manners. In a preferred aspect of the invention,light-sensitive silver halide or a mixture of such halides isprecipitated in an aqueous photographic gelatin solution. The resultingemulsion or dispersion retains the protective colloid and otherproperties of the gelatin of photographic grade. To the precipitatedsilver halide emulsion, which can be washed, ripened, etc., there areadded suitable sensitizers and, if desired, other emulsion adjuvants,and the emulsion is digested. To the digested emulsion are adde,separately or simultaneously, an aqueous solution or dispersion of thepolyvinyl pyrrolidone and of the water-insoluble vinyl addition polymer.After an intimate mixture is obtained, the resulting tricomponentcolloid-silver halide dispersion is coated on a suitable support, e.g.,a hydrophobic film base, and the coating dried. Additional gelatin canbe 1 added along with the other two colloids to provide the requiredamount of gelatin in the final silver halide emulsion or dispersion.

After drying, the light-sensitive silver halide layer is given asensitometric exposure through a neutral density wedge, processed bydeveloping, fixing, etc., and the image densities are read on aconventional type of densitometer. The unique tricompone-tgelatin/polyvinyl pyrrolidonefiwater-insoluble vinyl polymer silverhalide emulsion yields a clear film which is permeable to aqueousdeveloping and fixing solutions as is an allgelatin film and hascomparable photosensitometric properties because of the similarity insilver halide grain structure and size distribution. However, itsphysical, di-

mensional and practical photographic handling properties are markedlyimproved. For example, the humidity coefficient of expansion and sizechange during processing of the light-sensitive silver halide to asilver image is markedly reduced. The optical density of the image inpassing from the -wet to the dry state is markedly stabilized so that afinal dry optical density can be accurately predicted from a wet opticaldensity reading. Further, the knife etching character of this binder isgreatly improved from that of an all-gelatin film or a film containinggelatin and one of the other two colloid binding agents so that muchgreater etching control is possible. The drying rate of the processed,exposed film is increased, the tendency to curl at low hurniditiesreduced, and the impact resistance and anchorage substantially improved.These combinations of properties and results are surprising and are ofcommercial importance in graphic arts photographic films where thickemulsion layers are often used for continuous tone reproduction.

In a preferred aspect of carrying out the invention, there can be addedto the gelatino-silver halide emulsion a cationic optical sensitizingdye and a latex of the waterinsoluble vinyl polymer dispersed therein bymeans of an amphoteric dispersing agent, preferably an amphotericalkyliminodicarboxylate or alkylaminomonocarboxylate dispersing agent ofthe formula:

RNI-I [CH CH OOOM] p where R is an alkyl group of 12-18 carbon atmos, mis or 1, p is 2-111 and M is a cation selected from the group consistingof hydrogen, sodium, potassium and ammonium. In general, the dispersingagent is used in an amount from 0.5% to 15.0% by Weight of thewaterinsoluble vinyl polymer.

Suitable amino acid dispersing agents are disclosed in U.S. Patent2,816,920, Dec. 17, 1957, and are commercially available. Two of thesedispersing agents of particular interest are disodium N-tallowbeta-iminopropi-onate'and the disodium salt ofN-dodecyl-beta-iminodipropionate. In the case of the former dispersingagent, tallow represents a mixture of the alkyl radicals oleyl,palmityl, stearyl and myristyl in order of decreasing concentration. Nonionic as well as cationic surfactants can be used, but best results canbe obtained, especially in the case of the panchromatic silver halideemulsions, by means of the amphoteric alkyliminodicarboxylate dispersingagents described above.

The polyvinyl pyrrolidones useful in the emulsion can vary over a fairlywide range of average molecular weight but have an average molecularweight between 10,000 and 150,000. Higher average molecular weightsstill bring about improvements in certain characteristics of the filmbut haze sometimes is encountered as the molecular weight increasesbeyond the preferred range. With molecular weights below the preferredrange, the desirable effects are less pronounced since the lowermolecular weight material tends to diffuse out of the emulsion duringphotographic processing of the coated element.

Considerable latitude is possible in the choice of the colloiddispersion of the water-insoluble vinyl polymers, including copolymers.A preferred class are the alkyl acrylates and methacrylates, e.g.,polymers and copolymers of methyl, ethyl, butyl, ethylhexyl acrylate ormethyl and butyl methacrylate. Also, acrylic or methacrylic acid can beused in the preparation of useful copolymers. With 'most co-monomers, nomore than mole percent of such an acid is used in the polymerizationwith the other constituents so that the copolymer will'remainwater-insoluble. Other useful classes of vinyl monomers used to preparewater insoluble polymer and copolymer dispersions useful in accordancewith this invention are [the vinyl esters such as the acetate,propionate, etc.; the vinyl and vinylidene halides such as yinylidenechloride; styrene and substituted styrenes; the dienes such as another.

4- butadiene; .acrylon'itrile; ialkenes such as ethylene or propyleneand the like. I The water-insoluble polymers are free from color-formernuclei or groups.

In general, the 'best results are obtained with vinyl monomers whichyield the lowest water sensitivity and lowest modulus of elasticity.Thus, acrylates in general are preferable to methacrylates andpolyethylene to polyvinylidene chloride polymers and copolymers. Thevinyl polymers, in general, have an average molecular weight above10,000.

The particle size of vinyl dispersion is important, since the intendedapplication requires freedom from lightscattering. In general, particlesizes below the wave length of light, i.e., below 400 m would bepreferred. This may be controlled by techniques of emulsionpolymerization known in the art such as the use of adequateconcentrations of surfactants, the mode of stirring, the concentrationsof reactants, temperature, rate of additions of monomers, etc.

In order to realize the full advantages of the improved dimensionalstability of the emulsions of this invention, it is desirable to coatthe emulsions on a film base support which also has adequate dimensionalstability, e.g., polymethylene terephthalates, polystyrene,polycarbonates, e.g., the polycarbonate of 2,2-bis-p-hydroxypheny-lpropane, polyethylene terephthalate/isophthalate, etc. In general thepolyester films include those prepared from highly polymerized esters ofterephthalic acid and at least one glycol of the formula HOCH WCH OHwhere W is polymethylene or .alkyl-substituted polymethylene of 0 to 8carbons, e.g., 2,2-dimethylpropylene-1,3 or a cycloalkylene radical of 5to 6 carbon atoms, e.g., cyclopentyl-1,3, and cyclohexyl-1,4. Polymericfilms comprising up to 20 mole percent -of aliphatic dioarboxylic acidsbased on total moles of acids, e.g., succinic,

glutaric, adipic, hexahydroterephthalic and sebacic acids, in additionto at least 15 mole percent terephthalic acid, are also useful. 1

The above-described polymers or copolymers may contain a number, e.g., 1to 12 or more, of ether groups in the polymer chain. Such ether groupsmay be added as part of ether containing glycol derivatives or formed byside reactions during polymerization. Also the emulsions may becoated onvarious films and plates composed of glass, metal, e.g., aluminum,various waterproof papers, cellulose derivatives, e.g., celluloseacetate, cellulose propionate, cellulose butyrate, celluloseacetate-butyrate, and cellulose nitrate; other superpolymers, e.g.,nylon, polyvinyl chloride, poly(vinyl chloride 00 vinyl acetate), etc.

The polymer dispersions used in a preferred embodiment of this inventionare prepared in a conventional manner, starting with a polymerizableliquid monomer. This monomer is emulsified with water by means of thedispersing agents described above, and subjected to a conventionalemulsion polymerization using a free radical initiator, e.g. peroxide ora,or.'-aZ0 bis-(isobutyronitrile). In Procedure A, to follow, there isgiven a description of the preparation of a particularly preferreddispersion, that of polyethylacrylate. Alternately one can use a bulkpolymerization and prepare the dispersions by dispersing the moltenpolymer in water in the presence of a dispersing agent, such as iscommonly done with polyethylene.

The invention will be further illustrated by, but is not intended to belimited to, the following procedures and examples wherein the coatingswere evaluated as follows for their humidity coefficient of expansion,dimensional stability, knife etchability, adhesion and curl:

In determining humidity coefiicient of expansion, a 30 inch strip of acoating is scribed with a sapphire microgroove stylus so as to produce,near each end of 'the strip, fiducial marks which will be in closeproximity to the fiducial marks of a calibrated Invar plate when thestrip and Invar plate are brought into contact with one The strip isthen conditioned for 24 hours at a constant temperature and humidity andthen, while maintained at the same conditions, placed in flat contactwith the Invar plate. Two Gaertner filar micrometer microscopes, havinga total magnification of 100 diameters and micrometer least count 2 10-inches, are mounted so that measurements may be obtained by means of agraduated glass scale of distances between the fiducial marks on thecoating strips and the corresponding fiducial marks on the Invar plate.The Invar plate, microscopes and coating strip are all housed in aconditioning cabinet equipped with arm ports and viewing windows. Byvector addition of these distances and the known distance between thefiducial marks on the Invar plate, the distance is determined betweenthe two fiducial marks on the strip at a known humidity. The process isrepeated, with 24 hour preconditioning, to determine the distancebetween the stripss two fiducial marks at another known humidity. Thechange in length at the two humidity values divided by the average ofthe two lengths and divided by the difference in percent relativehumidity gives the humidity coefficient of expansion. Invar is anickel-steel alloy. Dimensional stability in terms of processing sizechange is determined in a very similar manner. Distance between fiducialmarks is determined on a coating strip which has been conditioned underconstant temperature and humidity for 24 hours. The strip is thenconventionally processed and dried, conditioned at the previous constanttemperature and humidity for 24 hours, and measured to determine thechange in distance between fiducial marks. The processing size change iscalculated by dividing this change in distance by the average distance.

Knife etching is a subjective test wherein the etcher rates variousmaterials on the basis of his ability, by means of a knife, to producesmooth gradations in density from high to low from an area having anoriginal high image density. Chipping, cracking, flaking, adhesivefailure etc., would cause a poor rating in terms of knife etchability. 7

Values of impact strength under various conditions were obtained usingan apparatus similar to that described by R. D. Spangler and E. B.Cooper, Journal of Applied Physics, vol. 28, No. 3, March 1957, pages329-333. In this apparatus, the measured quantity is the amount ofenergy absorbed by a film when a steel ball is projected through it. Bymeans of photoelectric cells, the velocity of a steel ball in freeflight can be compared with its velocity after having passed through thefilm being examined.

Dry adhesion of emulsion to the support was measured by the common testwherein cross-hatched lines are cut through the emulsion and a piece ofpressure-sensitive tape is applied to an emulsion surface and thenrapidly pulled off. Removal of a part of the emulsion from the baseindicates inferior anchorage. Wet anchorage can be determined similarlyafter normal photographic processing, by determining the tendency of thewet emulsion to lift off the base when a force is applied tangentiallyat the edge of the cross hatched lines.

Curl was measured by determining the weight required to restore a 10 x12" sheet of film conditioned at 20% RH. and 75 F. to a flat condition.

PROCEDURE A A 22-liter fluted reaction pot was equipped with athermometer, anchor stirrer, three-neck adapter containing a gas inlettube and two reflux condensers. The system was purged with nitrogen for10 to 20 min. and maintained under a positive nitrogen pressurethroughout the polymerization. To the pot were added 10 liters ofdistilled water, 484 g. of disodium-N-tallow-fl-iminodipropionate flakes(96%) and 50 g. of gelatin (used as a thermal stabilizer) with 1040 ml.of distilled water. The mixture was allowed to soak at room temperaturewith 6 moderate agitation for 10-15 minutes. The stirred reactionmixture was heated by a water bath to 50-55 C. for 15-20 min. to effectsolution. To the aqueous solution in the pot was added 3300 g. of ethylacrylate (from which the polymerization inhibitor had been removed byextraction with alkali). The stirred reaction mixture was heated by awater bath to -85 C., held for 10 min. in this temperature range andcooled to 75 C. To the reaction mixture was added 60 ml. of a 30% byweight aqueous solution of hydrogen peroxide and the temperature washeld at 75 C. until the polymerization initiated. After the initialexothermic reaction had subsided (note: moderated with cold water asrequired to control excessive foaming), 1700 g. of ethyl acrylate wereadded to the pot. The bath temperature was adjusted to 75i3 C. and 19ml. of a 30% by weight aqueous solution of hydrogen peroxide was added.After the second stage of the polymerization had subsided, thetemperature was raised to 80-85 C. and held in this range for 2 hours.The dispersion was then heated to 90 C., held for 10 min. and steamdistilled for 1 to 2 hours to remove any residual monomer. Thedispersion was cooled to about 50 C. and filtered through felt to removeany residue. The composition by weight of the dispersion made by thisprocedure is 30% polyethyl acrylate and 2.79% disodium-N-tallow-p-iminodipropionate.

PROCEDURE B A 22 liter fluted pot was equipped as described in ProcedureA and purged with nitrogen in the same manner. To the pot were added 8liters of distilled water and 16.7 g. of a high molecular weightpolyacrylamide (thermal stabilizer), which was added slowly through along stem funnel of narow bore and washed in with 2.5 liters ofdistilled water. The mixture was stirred for 2 to 3 hours at roomtemperature to effect solution. To the solution of polyacrylamide in thepot were added 667 g. of a 30% by weight aqueous solution of sodiumlauryl sulfate which was washed in with 400 ml. of distilled water, 1000g. of ethyl acrylate (from which the polymerization inhibitor had beenremoved by extraction with alkali). The stirred reaction mixture washeated by a water bath to.80 C.; for 10 min. in this temperature rangeand cooled to 75 C. To the reaction mixture was added 16 ml. of a 30% byweight aqueous solution of hydrogen peroxide :and the temperature washeld at 75 C. until the polymerization initiated. After the initialexothermic reaction had subsided (note: moderated with cold water asrequired to control excessive foaming), 1000 g. of ethyl acrylate and 16ml. of a 30% by weight aqueous solution of hydrogen peroxide were addedand this process was repeated until the total amounts of ethyl acrylateand hydrogen peroxide added were respectively 5000 g. and 80 ml. Afterthe fifth stage of the polymerization had subsided, the dispersion wastreated as shown in Procedure A to complete the polymerization andremove the residual monomer. The composition by weight of the dispersionmade by this procedure is 30% polyethyl acrylate and 1.2% sodium laurylsulfate.

PROCEDURE C A 22-liter fluted pot was equipped as described in ProcedureA and purged with nitrogen in the same manner. A solution of highmolecular weight polyacrylamide (thermal stabilizer) was prepared asdescribed in Procedure B. To the solution of polyacrylamide in the potwere added 667 g. of a 30% by weight aqueous isopropanol solution of asurfactant of the formula 0 a e 0 H3) 2C Hz-C o H ng- 001120112) noSOBNa which was washed in with 400 ml. of distilled water. A two stagepolymerization was carried out as described in Procedure A except thatbutyl acrylate was used in place of ethyl acrylate. The composition byweight of the dispersion made by this procedure is 30% polybutylacrylate and 1.2% polyether sulfate surfactant.-

PROCEDURE D Procedure C was essentially repeated except that 800 g. of a25% by weight aqueous solution of Tamol 731 (.registered trade name,Rohm & Haas, defined by Haynes, Chemical Trade Names and CommercialSynonyms, 2nd edition, 1955, Van Nostrand and Co., New York, as thesodium salt of a carboxylated polyelectrolyte) which was washed in with267 ml. of distilled water was used in place of the sodium salt of apolyether sulfate surfactant. A two-stage polymerization was carried outas described in Procedure A except that .methyl methacrylate was used inplace of ethyl acrylate. The composition by weight of the dispersionmade by this procedure is 30% polymethyl methacrylate and 1.2% sodiumsalt of carboxylated polyelectrolyte.

PROCEDURE E Procedure C was essentially repeated except that 200 g. ofsodium stearate which was washed in with 867 ml. of

distilled water was used in place of the sodium salt of an alkyl arylpolyether sulfate. A two stage polymerization was carried out asdescribed in Procedure A except that styrene was used in place of ethylacrylate and the bath temperature was 80 C. instead of 75 C. Thecomposition by weight of the dispersion made :by this procedure is 30%polystyrene and 1.2% sodium stearate.

PROCEDURE F Procedure A was essentially repeated except that 716 g. of a28% by weight aqueous solution of a surfactant of the formula which waswashed in with 714 ml. of distilled water, was used in place ofdisodium-N-tallow-fi-iminodipropionate. A mixture of monomers consistingof 3500 g. of vinylidene chloride and 1500 g. of 2-ethylhexyl acrylatewas used in place of ethyl acrylate.

An aqueous solution of 33.3 g. -of ammonium persulfate dissolved in 100ml. of distilled water and an aqueous solution of 16.7 g. of sodiummetabisulfite dissolved in 50 ml. of water were used in place ofhydrogen peroxide. The polymerization was carried out at 25- 30 C.instead of at 75 C. The composition by weight of the dispersion made bythis procedure is 21%/9% copolyvinylidene chloride/Z-ethylhexyl acrylateand 1.2% sodium salt of the alkyl aryl polyether sulfonate surfactant.

PROCEDURE G Procedure A was essentially repeated except that 333 g. ofisooctyl phenyl polyethoxy ethanol which was washed in with 1190 ml. ofdistilled water was used in place ofdisodium-N-tallow-B-iminodipropionate. The composition by weight of thedispersion made by this procedure is 30% polyethyl acrylate and 2%isooctylphenylpolyethoxy ethanol.

8 PROCEDURE H To a 2-liter beaker was added 600 g. of pellets of acommercially available polyethylene having a melting point in the rangeof 101-105" C. and a viscosity at 140 C. of 160 cps. The material wasslowly melted with intermittent stirring and raised to a temperature ofC. at which time g. of olcic acid was added with thorough stirring. Atthe end of the addition there was a 5 lowering of temperature. After thetemperature was again raised to 130, 120 g. of distilled morpholine wasstirred in and the temperature (which had dropped to about 122) wasraised to 127. Over a period of 3-4 minutes the liquid was added, withvigorous stirring, to a 4-liter beaker containing 2800 g. of distilledwater which had been preheated to a temperature range of 97-99 C. Thedispersion thus prepared was allowed to cool slowly to 87", then cooledin cold water and finally ice water to 30 C. It was then filteredthrough felt to remove any hard residue. The composition by weight ofthe dispersion made by this procedure is 17.7% polyethylene and 4.9%morpholine oleate.

Example I A photographic emulsion was precipitated and ripened in aconventional way and freed of unwanted soluble salts by a coagulationand wash procedure taught in Example I of Moede, US. 2,772,165. Thesilver halide composition was 96.3 mole percent AgBr and 3.7 molepercent AgI in the presence of 14.7 g. of gelatin per mole. Thecoa-gulated emulsion was redispersed in water in the presence ofadditional gelatin, digested at elevated temperatures in the presence ofconventional sulfur sensitizers, cooled and stabilized withpost-sensitization additives common in the art such as additionalhalide, antifoggants etc. It was then divided into seven equal portionsand to six of these portions there was added, with good stirringadditional gelatin, a 40% by weight aqueous solution of poly-N-vinylpyrrolidone (PVP) having an average molecular weight of 40,000 and anaqueous dispersion containing 30% by weight polyethyl acrylate as wasprepared under Procedure A. The final binder compositions in eachportion were as shown in Table I. To portion No. 1, serving as acontrol, only gelatin was added.

These emulsions were applied at a silver halide coating weight of 110mg./dm. (calculated as silver bromide) onto 7-mil thick polyethyleneterephthalate film base hearing a substratum of a vinylidene chloride/methyl acrylate/ ita conic acid copolymer such as is described inExample IV of Alles patent, US. 2,779,684 and over this a secondsubstratum containing 0.5 rng./dm. of gelatin. The emulsions were thenevaluated for various physical characteristics by tests alreadydescribed using a relative scale in which A represents the mostdesirable and D the least desirable relative rating for the intendedapplications. Such letters indicate a subjective averaging of numericalvalues obtained under a variety of conditions. Results are shown inTable I. f

TABLE I.BINDER COMPOSITION PHOTOGRAPHIC PROPERTIES Percent Wet-to- KnifeImpact Dimen- No. Percent Percent Polyethyl Relative Contrast Dry Etch-Curl Resistsional Anchorage Drying Gelatin PVP Acrylate Speed Densitying anee Stability Rate Dispersion Change In Table I, the sensitometricdata was obtained from film strip samples of the coatings which weregiven a 20 second, intensity-scale, sensitornetric, step-wedge exposureto a White light tungsten source. The exposure in each and F. To thesixth portion, serving as a control, only gelatin was added. Uponcoating and evaluation as described in Example I, improvement wereobtained, shown in Table II, similar to those Example I except that thesuccessive step increased by the factor of the square-root- 5 balance ofcertain properties varied with the particular of two. The exposed filmstrips were developed for 3 dispersion used.

minutes in a developer of the following composition to The polystyrenesample had an average particle size determine its sensitometriccharacteristics: greater than the other polymers.

TABLE II Relative Wct-to-dry Knife Dimen- Impact WaterInsolubleVinylPolymer Dispersing Agent Speed Density Etching sional CurlStrength Anchorage Change Stability Polyethyl acrylate Alkylimino-dipropionate... 2.2 +.06 A. Polybutyl acrylate Alkyl arylpolyether sulfate 2. 5 02 A. Polymethyl niethacrylate Polycarboxylate 2.5 02 C. Polystyrene Sodium stearate 2.5 11 C. Copolyvinylidenechloride/2- 'Alkyl aryl polyether sul- 2.1 07 A. ethylhexyl acrylate.ionate. None (Control) None 1.0 .14 D.

G. Example III y gj g f Sulfate 3% An emulsion was prepared according tothe procedure g eslccae of Example I and divided into three parts. Toeach 68 32 24'() part was added a polyethyl acrylate dispersion prepared2 according to Procedure A and a solution of polyvinyl g pyrrolidone ofvarying molecular weights. Evaluation W KT was carried out as describedin Example I. Binder commer to ma 6 positions and resulting propertiesare shown in Table III.

TABLE III Percent Percent Percent Approx. M01. Wet-to-dry KnifeDimensional Impact Gelatin PVP Polyethyl Wt. PVP Speed Density EtchingStability Resistance Curl Acrylate Change 100.0 1.0 .14 C C o D 55. 5 1133 10, 000 1.8 09 B A o o 55. 5 l6. 5 28 40,000 2. 2 06 A B B B 55. 5 2222. 5 350, 000 2. 9 +0. 3 o B C 0 After development, the strips weretreated in a conven- While the molecular weight of the polyvinylpyrroltional acid hardening and fixing bath containing 153 g. idoneappears to have a quantitative effect favoring an anhydrous Na S O perliter, washed in tap water and intermediate molecular weight,improvements are possible dried in a conventional manner. Opticaldensities of the over a wide range of molecular weights provided thepolyfilm strips were read at each exposure step on a Western vinylpyrrolidone is water soluble and the concentrations Electric RA-110 0Cdensitometer, the readings being made of latex and gelatin are properlybalanced for the parboth at the start of the drying period when thefilms were ticular polyvinyl pyrrolidone. The haze level was conwet andat the end of the drying peniod. The et t -dr sidered undesirable in thecoating employing the polydensity changes recorded in the tablescorrespond to dry vinyl pyrrolidon f m l c l r W ight. Foroptictaldensifies f approximately 2.0. Anegative or posisome lesscritical applications this haze level may be tive sign for this densitychange indicates a loss or gain, t l rable. respectively, of density ondrying. All the films in this Example IV exam le includin the controlwith an allelati b der had g g g n In An emulsion was prepared as inExample II, half of These results indicate the binder composition ofthis g i i t a the l a l g i invention yields improvements in most ofthe critical proper f j 52. z Was emu 9' 1 ei'ties required inphotographic films, in particular for o fl a samle g i those used ingraphic arts applications; As can be noted, S g I one u [on 39 a 9 y i 5different balances of properties are attainable for difterf accor .1 5 ifii ent ratios of the three binder components with the coating 5 2 5 T ig 10111 lweld y f i i =frorii emulsion portion No. 5 representing thebest overlat ge a n p0 yvmy Pyrm 1 one p0 ye y all balance. y

Example H d A similar but higher contrast emulsion was prepared withvariations of ripening and digestion conditions in the An emulsion wasprepared as in Example I and was manner customary in the .art. As in theparagraph above, divided into six portions. To each of five portionswere half of this emulsion contained gelatin as the only binder added a40% by weight aqueous solution of polyvinyl material, while the otherhalf was treated by adding the pyrrolidone (M.W.=40,00O) and an aqueousdispersion same amounts of a polyvinyl pyrrolidone solution and ofcontaining 30% by weight of various water insoluble vinyl a polyethylacrylate dispersion.

polymers so that the final binder solids composition by The fouremulsions were coated as in Example I exweight would be 55.5//28,gelatin/polyvinyl pyrrolicept that the film base support had coated onthe reverse done/dispersed polymer. The dispersions used were preside anantihalation backing containing no silver halide pared, respectively,according to Procedures A, C, D, E, 7 but with binder composition andcoating weight identical to the emulsion binder. Evaluation as inExample I gave the results shown below in Table IV.

ene of to 8 carbons, e.'g., 2,2-dimethylpropylene-1,3 or a cycloalkyleneradical of to 6 carbon atoms, e.g., cyclo- TABLE IV Percent Wet-to-DryHumidity Coating Percent Percent Polyethyl Relative Contrast DensityKnife COOfllClCllt Impact Anchorage Gelatin PVP Acrylate Speed ChangeEtching of Expan- Strength sionXlO Low Contrast Control 1.0 1. 0 10 3. 5D B. Low Contrast Coating 2.0 1. 0 +.01 2. 7 A A. High Contrast Control1.0 1.4 12 3. 5 D B. High Contrast C0ating 1. 5 1.4 0 2. 7 A A.

Example V An emulsion was prepared similar to that in Example I exceptthat a symmetrical thiocarbocyanine ethiodide optical sensitizing dyewas added during digestion to render it panchromatic. The emulsion wasdivided into three portions and an aqueous solution of polyvinylpyrrolidone and an aqueous dispersion of polyethyl acrylate were addedto each portion. The final binder composition of the first portion wasidentical to that of the first portion of Example II wherein thepolyethyl acrylate polymer was dispersed with an amphoteric dispersingagent, disodium-N-tallowabeta-iminodipropionate (Procedure A). Thesecond emulsion portion was the same except that the polyethyl acrylatewas dispersed with an anionic surfactant, sodium lauryl sulfate(Procedure B). The third emulsion portion was the same except that thepolyethyl acrylate was dispersed with a nonionic agent, isooctylphenylpolyethoxyethanol (Procedure G).

The three emulsions were coated as in Example I except that thepolyethylene terephthalate film base support bore only the singlecopolymeric substratum (i.e., the second substratum containing 0.5mg/dm. of gelatin was absent), and had good anchorage and gave resultssimilar to Examples I-IV.

Example VI The coating from emulsion portion No. 5 of Example I wasessentially duplicated except that the dispersed water-insoluble vinylpolymer used in the present example was polyethylene, prepared asdescribed in Procedure H. This coating, when compared with an allgelatin binder control by processing both films as described in ExampleI, was found to exhibit less wet-to-dry density change and improveddimensional stability.

In addition to the polymeric materials specifically disclosed in theexamples, there are various other materials which can be used to makeapproximately equivalent dispersions, e.g., polybutyl acrylate andcopolymers of ethyl acrylate, butyl acrylate or ethylhexyl acrylate, andacrylic acid containing less than about 10 mole percent of acrylic acid.These polymers are physically fairly soft. Other polymers are usefulequivalents in the practice of this invention but, because of beingrelatively harder, they are considered to be less desirable materials.Among these polymers, listed in order of decreasing physical hardness,are polymethyl acrylate and polyethyl methacrylate.

The present invention is not limited to the use of a particular filmbase support as the emulsions may be coated on various films and platescomposed of glass, metal, e.g. aluminum, cellulose derivatives, e.g.,cellulose acetate, propionate, butyrate, acetate-butyrate, and nitrate;superpolymers, e.g., nylon, polyvinyl chloride, poly- (vinyl chlorideco-vinyl acetate), polystyrene and polyesters such as the poly/methyleneterephthalates, polycarbonates, e.g., the polycarbonate of2,2-bis-p-hydroxyphenyl propane, polyethyleneterephthalate/isophthalate, etc.

Other useful polyester films include those prepared from highlypolymerized esters of terephthalic acid and at least one glycol of theformula HOCH WCH OH where W is polymethylene or alkyl substitutedpolymethylr pentyl-1,3, and cyclohexyl-1,4. Films comprising up to molepercent of aliphatic dicarboxylic acids based on total moles of acids,e.g., succinic, glutaric, adipic, hexahydroterephthalic and sebacicacids in addition to at least 15 mole percent terephthalic acid are alsouseful. The above described polymers may contain a number (e.g., 1 to 12or more) of ether groups in the polymer chain. Such ether groups may beadded as part of ether containing glycol derivatives or formed by sidereactions during polymerization.

Of course, various sublayers may be present to anchor the layer to thebase as is common in photographic film and plate manufacture. Also,various other auxiliary layers may be employed such as antiabrasionlayers and antihalation backing or undercoat layers.

The emulsions may be modified by the addition of general emulsionsensitizers, e.*g., alkyl thiourea, phenyl isothiocyanate, sodiumthiosulfate, and alkyl isothiocyanate; metal compounds e.g., of gold,platinum, palladium, iridium, rhodium, mercury, cadmium etc.;antifogging agents, e.g., Z-mercaptobenzothizole,l-phenyl-S-mercaptotetrazole, benzotriazole, triazindene, tetrazindeneand 5- nitrobenzirnidazole; sensitizing dyes; color formers (whichmight, alternatively, be in the developer solution); hardeners, e.g.,formaldehyde and other aliphatic aldehydes, dimethylol urea, trimethylolmelamine; chrome alum and other chromium compounds, coating aids, imagecolor modifiers, brightening agents, colorants, e.g. pigments, mattingagents and other emulsion adjuvants.

Photographic requirements of graphic arts emulsions are generally bestmet by silver halides in which the predominant halide is bromide. Up to10 mole percent iodide is added to vary the photographic behavior aswell as the usual chemical sensitizers and optical sensitizing dyes.However, the unique binder advantages of this invention such aswet-to-dry density stability, knife etchability, impact resistance,dimensional stability, and anchorage to the support are also applicablein varying degrees to other halides over a wide range of compositionsincluding silver chloride, chloro-bromide and iodo chlorobromideemulsions.

While these elements have their greatest usefulness in graphic artapplications, many of the unique properties would be advantageous inother photographic films, e.g., cine, X-ray, portrait and color films.They could be used in monolayer or multilayer coated products. Ingeneral, these elements would be applicable to special processingvariations used with conventional films, e.g. for dye inhibition filmsor preparing planographic printing plates.

This invention has the advantage of providing superior photographicemulsions for the manufacture of films having improved physicalproperties and improved wetto-dry optical density stability of thedeveloped image. Films made according to the present invention do notsuffer the disadvantage of loss of optical density of the developedimage during drying of the film. Among the improved physical properties,dimensional stability is particularly significant but improvedflexibility and improved anchorage are also important. These advantageshave been achieved without sacrifice in sensitometric or other physicalproperties of the film; in fact, photographic speed, as can be seen inEx. I, is significantly increased. The preferred classes of ionicdispersing agents disclosed in this invention make possible theformation of polymer particles of sufficiently small size to provide atransparent film when mixed with gelatin, coated and dried.

The particularly preferred amphoteric dispersing agents used in thepanchromatic emulsions, in contrast to the anionic and cationicsurfactants used in previously disclosed products, do not interfere withdye sensitization. A further advantage is the simplicity of the processof this invention; since the additions are in the form of aqueoussolutions and dispersions, the process can be carried out simply andeconomically on a commercial scale with no need for elaborate equipmentsuch as solvent recovery systems.

Polymers are often incompatible and, therefore, mixtures of two or threepolymers cause difficulties where clarity is desired, as in photographicfilms. There are no reliable rules known in polymer science forpredicting when compatibility will occur or what balance of propertiesthe final polymer mixture will have. According to the present invention,however, applicants have provided a mixture of three different polymersand have found them \to be compatible and to give photographic emulsionshaving excellent optical clarity as well as other useful photographicand physical properties.

We claim:

1. A photographic gelatino-silver halide emulsion comprising (l) anaqueous phase containing therein as a part of said phase (a) gelatin and(b) a water-soluble polyvinyl pyrrolidone having an average molecularweight of at least 8,000 and (2) a dispersion therein ofwater-dispersible colloidal particles of a substantially water-insolublevinyl addition polymer of an ethylenically unsaturated monomer ofmolecular weight less than 250, said gelatin, polyvinyl pyrrolidone randwater-insoluble polymer being present in the percentages by weight from30% to 80%, 6% to 30% and 10% to 55%, respectively, of the total Weightof the three polymeric binders.

2. An emulsion according to claim 1 wherein said colloidal particleshave an average diameter of less than 400 mu and an average molecularweight above 10,000.

3. A photographic emulsion layer formed from an emulsion defined inclaim 1.

4. An emulsion layer according to claim 3 wherein said polyvinylpyrrolidone is poly-N-vinyl py-rrolidone having an average molecularweight from 10,000 to 150,000.

5. An emulsion layer according to claim 3 wherein the sum of the lightabsorbed and scattered by the combination of the three polymeric bindercomponents in the absence of silver and silver salts corresponds to anoptical density of not more than 0.1.

6. An emulsion layer according to claim 3 wherein said water-insolublevinyl addition polymer is a polyalkyl acrylate.

7. An emulsion layer according to claim 3 wherein the silver halides is10 to 99 mole percent bromide, to 90 mole percent chloride, and 0 to 10mole percent iodide. 8. An emulsion layer according to claim 3containing an amphoteric dispersing agent of the formula:

where R is an alkyl group of 1218 carbons, m is one of the numbers 0 and1, p is 2-m and M is a cation selected from the group consisting ofhydrogen, sodium, potassium and ammonium.

9. An emulsion layer according to claim 3 wherein said halide is silverbromoiodide.

10. A photographic film comprising a film supportbearing an emulsionlayer as defined in claim 3.

11. A photographic film comprising a dimensionallystable hydrophobicfilm support bearing on one surface an emulsion layer as defined inclaim 3.

12. A photographic film according to claim 10 having on the othersurface an antihalation, anti-curl backing layer.

13. A process for preparing a modified gelatino-silver halide emulsionwhich comprises adding to a silver halide emulsion precipitated ingelatin, after digestion, an aqueous solution of a Water-solublepoly-N-vinyl pyrrolidone and an aqueous dispersion of colloidalparticles of a substantially water-insoluble vinyl addition polymer ofan unsaturated monomer of molecular weight less than 250 to form anemulsion containing said polymeric components in the percentages byweight of 30% to 6% to 30%, and 10% to 55%, respectively, of the totalweight of said components.

14. A process according to claim 13 wherein the polyvinyl-N-pyrrolidoneand the water-insoluble polymer are added separately.

15. A process according to claim 13 wherein the polyvinyl-N-pyrrolidoneand the water-insoluble polymer are admixed and the mixture added to thegelatino-silver halide emulsion.

References Cited by the Examiner UNITED STATES PATENTS 2,698,794 1/1955Godowsky 96-98 2,964,405 12/1960 Talbot et a1. 96-114 3,000,740 9/1961De Belder et a1 96-1l4 3,000,741 9/1961 De Pauw et a1. 96114 FOREIGNPATENTS 536,673 4/1955 Belgium. 793,549 4/ 1958 Great Britain.

OTHER REFERENCES Evva: Chemical Abstracts, vol. 52, pages 88089 1958)NORMAN G. TORCHIN, Primary Examiner.

HAROLD N. BURSTEIN, Examiner.

J. T. BROWN, Assistant Examiner.

1. A PHOTOGRAPHIC GELATINO-SILVER HALIDE EMULSION COMPRISING (1) ANAQUEOUS PHASE CONTAINING THEREIN AS A PART OF SAID PHASE (A) GELATIN AND(B) A WATER-SOLUBLE POLYVINYL PRRROLIDONE HAVING AN AVERAGE MOLECULARWEIGHT OF AT LEAST 8,000 AND (2) A DISPERSION THEREIN OFWATER-DISPERSIBLE COLLOIDAL PARTICLES OF A SUBSTANTIALLY WATER-INSOLUBLEVINYL ADDITION POLYMER OF AN ETHYLENICALLY UNSATURATED MONOMER OFMOLECULAR WEIGHT LESS THAN 250, SAID GELATIN, POLYVINYL PYRROLIDONE ANDWATER-INSOLUBLE POLYMER BEING PRESENT IN THE PERCENTAGES BY WEIGHT FROM30% TO 80%, 6% TO 30% AND 10% TO 55%, RESPECTIVELY, OF THE TOTAL WEIGHTOF THE THREE POLYMERIC BINDERS.